Lubricants containing stabilized dispersions of fatty acid salts



LUBRICANTS CDNTAINING STABILIZED DISPER- SICNS F FATTY ACID SALTS Arnold J. Morway, Clark, NJ., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. 1 Filed Oct. 1, 1957, Ser. No. 687,366

"'8 Claims. (Cl. 252-405 This invention relates to lubricating oil compositions. Particularly, it relates to lubricating fluids and semi-fluids containing metal salt of low molecular weight fatty acid and a synthetic ester.

Alkaline earth metal salts of C to C fatty acids, parever, for some applications, these prior methods are not wholly satisfactory. Thus, the presence of higher molecular weight salts or soaps result in high deposit formation when the lubricant is used as a crank-case lubricant, while the emulsion type materials are rather corrosive because of their water content and are also somewhat unstable, tending to separate upon storage. It has also been proposed to dehydrate the emulsion type of material, but

while this reduces the danger of corrosion, it still results in an unstable product and unless the dehydration is carefully controlled a grainy unsatisfactory dispersion is obtained.

It has now been found that metal salts of low molecular weight fatty acids may .be stably dispersed in the presence of a synthetic ester. In this manner, simple lubricating dispersions can be formed which have excellent extreme pressureproperties and good load-carrying characteristics.

The metal salts operable in the invention will include v alkaline earth metal salts such as calcium, barium, strontium, etc. of low molecular weight C -C fatty acids such as, acetic acid, propionic acid and butyric acid. Specific examples of these salts will include calcium acetate, calcium butyrate, barium acetate and barium propionate.

The synthetic esters used to stably disperse the salt are "those estersco'nsisting of aliphatic saturated hydrocarbon chains interlinked by one or two ester linkages and containing a total of about 15 to 40, e.g. 20 to 35, carbon atoms. Such esters will include simple esters and diesters prepared from C to C alkanols or C to C glycols with either C to C alkanoic acids or C to C alkanedioic acids. Preferred esters are those prepared from alkanedioic acids and Oxo alcohols. The Oxo alcohols are isomeric mixtures of branched chain primary alkanols produced by the reaction of an olefin with hydrogen and carbon monoxide in the presence of a cobalt catalyst to form a mixture of aldehydes, which aldehydes are then hydrogenated to form the Oxo alcohol. Such Oxo alcohols and their preparation are well known in the art.

Specific examples of esters of the above types will include diesters such as: di-(C Oxo) adipate; di(2 -ethyl- .hexyl) sebacate; di-(C Oxo) sebacate; 1,6-hexamethylene glycol di-(Z-ethylhexanoate); 1,10-decamethylene glycol di-(caprylate); and simple esters such as: nonyl hepetc.

tanoate; decy-l laurate; octadecyl laurate; decyl steal-ate;

2,940,932 Patented June 14, 1960 The base .oil of the lubricating composition may be either a mineral lubricating oil, -a synthetic lubricating oil or both. Synthetic oils include: monoand di-esters prepared from alkanols or glycols with monoor dicarboxylic acids such as are described above; complex esters, e.g. the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid; esters of phosphoric acid; halocarbon oils; polyglycols; silicone oils; etc.

Particularly desirable synthetic oils are the silicone polymer oils having lubricating oil viscosity, i.e. viscosities of about 25 to 3500 SSU at 100 F. These oils have the general formula:

wherein R is a hydrocarbon radical, which may be halogen (e.g. chlorine) substituted or unsubstituted and including alkyl, aryl, haloaryl, alkylaryl, arylalkyl and cycloalkyl radicals containing between about 1 to 8 carbon atoms per radical. Specific examples of such oils include phenylmethylsilicone, dimethylsilicone and chloro-phenylmethylsilicone. These materials are known in the art and are available under trade-names such as DC (Dow Corning) F-258 Silicone Fluid, DC F-6O Silicone Fluid and DC 550 Silicone Fluid. A preferred silicone oil is Dow Corning 710 Silicone Fluid, which is a phenylmethylsilicone polymer oil having a viscosity at 25 C. of 500 centistokes.

Various additive materials can also beadded to the lubricating composition in amounts of about 0.1 to 10.0 weight percent, based on the total weight of the composition. Examples of such additives are: detergents such as calcium petroleum sulfonate; oxidation inhibitors such as phenyl-alphanaphthylamine; viscosity index improvers such as polyisobutylene; corrosion inhibitors such as sorbitan monoleate; pour depressants; dyes; and the like.

The compositions of the invention will therefore comprise lubricating oil, a wear. reducing amount of the metal salt and at least a sufiicient amount of synthetic ester to maintain said salt in a stable dispersion. In terms of weight percent, such compositions will usually comprise neutralizing the fatty acid with a metal base (-i.e. hy-

droxide or oxide) in the presence of the synthetic ester, followed by heating to temperatures of about 300 to 500 F. e.g. 300 to 400 F. in order to dehydrate the mixture. Lubricating oil, other than the synthetic ester, may also be present during the neutralization. Although the proportions of acid, base, ester and lubricating oil may be such as to form a finished lubricant, it is preferred to first make a concentrate and then to dilute the concentrate with additional lubricating oil to form the finished lubricant. To insure a completely homogeneous final lubricant, the lubricant may be homogenized in a Gaulin homogenizer, a Morehouse mill, a Charlotte mil-l, etc.

The invention will be further understoodby'the following examples which include preferred embodiments of the invention:

Example I :at. 210 R, were charged at a. fire heated kettle. 1,7

4 mate smooth, uniform slurry was formed. 25 weight percent of glacial acetic acid wasnext added, and the temperature rose to 210 F. due tov the heat of reaction. External heating was appliedv and V the mixture was heated to about 310 F, for about one hour until the product was completely dehydrated. The, product was then allowed to cool to about 200 F. and was then passed through a Charlotte mill to form a smooth prodnot having a semi-fluid consistency.

(B) For comparison purposes, a lubricant containing dehydrated calcium acetate was prepared in the manner of I(A) above, except that 50 weight percent of mineral lubricating oil was used and no ester oil was present.,

The products'of (A) and (B)'-above were each'tested for stability as follows: A quart sample bottle was filled with the lubricant and stored in an oven maintained at 210 F. for five days, after .which the sample was examined for salt precipitation. The product of (A),

4 Example VI weight percent of the product of Example V was intimately mixed with 75 weight percent of a mineral lubricating oil having a viscosity of 80 SUS at 40 F. This mixture was then passed through a Gaulin homogenizer operating at 6000 p.s.'i. shear.

l I flExample VII 7 20 weight percent of the base material of Example V was intimatelyv mixed with 80 weight percent of Dow Corning Fluid 7 10 (a phenylmethylsilicone polymer having-a-viscosity at 250 C. of 500 cs.). The mixture; was

then homogenized 'in a Gaulin homogenizer at 6000 -p.s.i.

shear.

' All of the products of the preceding examples were smoothly homogeneous compositions. The compositions in terms of initial ingredients, and the properties of the preceding examples of the invention are summarized in the following table: i I

Composition (Wt. Percent) Examples Glacial acetic acid Hydrated lime Dt-(Gm 0x0) adlpat Mineral lubricating Phenylmethylsilleon Properties:

(Jox1sisteney Viseoslt y(SSU)- I 1 100 F 210 F 4-Ball Wear 'lest (1,800 r.p.m

1 hour75 O.) mm. dia. scar e oil- .1: Chlorinated phenylmethylsillcone oil which contained the synthetic ester, showed nosalt precipitation. The product of .(B), which contained no ester, showed about -a one-eighth inch layer of precipitated salt on'the bottom of the sample bottle. It is thus seen that the presence of the ester stabilizes the salt dis persion. a

a Example II weight percent of the finaldehydrated product of Example I(A) was. intimately 'mixed with 70 weight percent of a mineral lubricatingoil having a viscosity ofabout 80 SUS at 210 F. This mixture was then passed A lubricant was prepared in a manner similar to that of Example'II except that 70 'weightpercent of Dow Corning Silicone Fluid 710 was used in place of the 70 weight per cent mineral oil. a p a Example IV ample IV which was a similar composition except that acetate.

.As seen from the preceding table,lubricants prepared 7 by dispersing anhydrous calcium acetate in the presence of'a' synthetic ester formed stable lubricants which had I very low wear characteristics. Examples I(A) shows that semi-fluids may be prepared in this manner, while Examples II, III and IV illustrate the formation of fluid type lubricants .preparedby further diluting the concentrate of Example I(A) with various lubricatingoils.

For comparison-purposes, a blend was prepared consistirig of the di-(C Oxo) adipate, mineral lubricating oil and phenylmethylsilicone oil in the same proportions as "in Example III, but which contained nocalcium mm. in the"4-.ball wear test, while the composition ofExit also; contained calcium acetate gave a wear scar di- 'ameter of 0310 mmi This illustrates the etfectivenessof 'theifatty' acid salt in reducing wear. The product of Example IV was also tested for storage stability'and showedvno sign of oil separation or salt precipitation Example III was repeated except that General'Electric 81406 Silicone Fluid was used in place of the Dow Corning Fluid. The GE. silicone was a chlorinated phenylmethyl silicone. l

Example V when stored for four weeks at F.

Example V illustrates a semi-fluid lubricant in which the synthetic'ester also served as the sole lubricating oil, while Examples VI .and VII again illustrate fluid materials formed. by further dilution of the concentrate of a I Example V with other lubricating oils.

16.75' weight percent of hydrated lime and 5825' weight percent'of a di-(C Oxo) .adipate' (theC Oxo alcohol was prepared from tripropylene) werecharged to. a steam-heated kettle and mixed to a smooth slurry.

.25 weight percent of glacial aceticv acid was slowly added while stirring and the temperature rose to 230 F. where large quantities of steam were evolved. The mixture was further heated to about 320 F. ,to completely dehydrate the vcalcium acetate. This base material was then cooled to about 200 F, at which point it was homo-' g'enized in a Gaulin homogenizer operating at 6000 p.s.i. shear, and then allowed to cool to room temperature.

tion can also be In summary, this invention relates to lubricants containing an anhydrous alkaline earth metal salt of a C: to C fatty acid which is stabilized against salt precipitation by a synthetic ester. Generally at least about 25 should be present. In cases where the ester is also a lubricating oil inits own right, then compositions'can be prepared consisting only of the anhydrous salt and the ester. Although the working examples thus farpresented. are only of anhydrous calcium acetate anda diester, other salts and esters contemplated by 'the invenreadily prepared in the same manne For example, a composition can be prepared consisting This blend gave a wear scar dia.; of 2.85

of 10.0 wt. percent anhydrous barium propionate, 15 wt. percent of n-octyl stearate and 75 wt. percent of mineral lubricating oil of 80 SUS viscosity at 210 F.

It is thus seen that excellent stable lubricants may be prepared containing synthetic ester and the metal salt of the C to C fatty acid as the sole metal salt component, i.e. without the necessity of having present higher molecular weight salts, e.g. calcium stearate or calcium petroleum sulfonate.

What is claimed is:

l. A lubricating oil composition consisting essentially of a lubricating oil, about 5 to 40 wt. percent of anhydrous alkaline earth metal salt of C to C fatty acid and about 2 to 50 wt. percent of a synthetic ester consisting of saturated aliphatic hydrocarbon chains joined by two ester linkages and containing a total of 15 to 40 carbon atoms.

2. A composition according to claim 1, wherein said synthetic ester is also a lubricating oil.

3. A composition according to claim 1, wherein said salt is calcium acetate.

4. A lubricating oil composition according to claim 1, wherein said lubricating oil is a mineral lubricating oil.

5. A lubricating oil composition according to claim 1, wherein said ester is a diester of a dicarboxylic acid and an alkanol.

6. A composition according to claim 1, wherein said salt is calcium acetate.

cating oil composition containing an anhydrous salt, followed by mixing until smooth.

8. The process according to claim 7, wherein said alkaline earth metal base is neutralized with said acid in a mixture of mineral lubricating oil and said synthetic ester.

References Cited in the file of this patent UNITED STATES PATENTS 2,079,051 Sullivan et a1 May 4, 1937 2,467,147 Morway et al. Apr. 12, 1949 2,581,127 Morway et al. Jan. 1, 1952 2,607,735 Sproule et al. Aug. 19, 1952 2,692,233 Cottle Oct. 19, 1954 2,744,870 Stillebroer et al. May 8, 1956 2,820,815 Matuszak et al. Jan. 21, 1958 FOREIGN PATENTS 744,685 Great Britain Feb. 15, 1956 

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A LUBRICATING OIL, ABOUT 5 TO 40 WT. PERCENT OF ANHYDROUS ALKALINE EARTH METAL SALT OF C2 TO C4 FATTY ACID AND ABOUT 2 TO 50 WT PERCENT OF A SYNTHETIC ESTER CONSISTING OF SATURATED ALIPHATIC HYDROCARBON CHAINS JOINED BY TWO ESTER LINKAGES AND CONTAINING A TOTAL OF 15 TO 40 CARBON ATOMS. 